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          <h2 class="post-title" itemprop="name headline">Java 内部类的定义和使用</h2>
        

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        <p>对于内部类的定义使用暂时不作为我们首要的类设计原则。</p>
<h1 id="内部类的基本概念"><a href="#内部类的基本概念" class="headerlink" title="内部类的基本概念"></a>内部类的基本概念</h1><p>所谓的内部类指的就是一个类的内部进行其他类嵌套的操作语法形式。理论上就跟盗梦空间一样，一层层进行类的嵌套定义。但是如果你进行类的嵌套定义太多了，那么自己也就晕了。</p>
<p>范例：内部类的基本使用</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> 内部类;</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Other</span></span>&#123;<span class="comment">//定义了一个外部类</span></span><br><span class="line">    <span class="keyword">private</span> String msg = <span class="string">"hello world!!"</span>;</span><br><span class="line">    <span class="comment">//+++++++++++++++++++++++++++++++++++</span></span><br><span class="line">    <span class="class"><span class="keyword">class</span> <span class="title">Inner</span></span>&#123;<span class="comment">//定义了一个内部类</span></span><br><span class="line">        <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">()</span></span>&#123;<span class="comment">//定义了一个普通方法</span></span><br><span class="line">            System.out.println(msg);<span class="comment">//调用msg属性</span></span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">//+++++++++++++++++++++++++++++++++++</span></span><br><span class="line">    <span class="comment">//定义一个外部类方法，这个方法负责产生内部类对象并且调用print()方法</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">fun</span><span class="params">()</span></span>&#123;</span><br><span class="line">        Inner in = <span class="keyword">new</span> Inner();</span><br><span class="line">        in.print();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Demo</span> </span>&#123;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String args[])</span></span>&#123;</span><br><span class="line">        Other other = <span class="keyword">new</span> Other();</span><br><span class="line">        other.fun();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>通过以上的代码立刻就可以发现一个问题：程序的结构有些混乱。虽然内部类破坏了程序结构从整体上来讲不好，但是从另外一个方面上来讲，内部类也是有优点的，在于外部类的私有访问。</p>
<p>范例:将程序的内部类提取到外部，要求实现同样的功能。</p>
<ul>
<li>Outer和Inner是两个独立的类，而且Inner类需要访问Outer类中的msg属性，但是Outer类中的msg属性使用了private属性进行了封装，所以封装的属性要被外部访问，那么需要写getter方法</li>
<li>在Inner类的print()方法中如果想要访问msg属性的内容，那么只能通过getmsg()的方法完成,getmsg()是一个普通方法，必须通过outer类对象才可以访问，那么这个时候需要把在主方法中的outer类对象传递到inner类里面；</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> 内部类<span class="number">1</span>;</span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Outer</span></span>&#123;</span><br><span class="line">    <span class="keyword">private</span> String msg = <span class="string">"hello world!"</span>;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> String <span class="title">getMsg</span><span class="params">()</span></span>&#123;<span class="comment">//通过这个方法才能取得msg属性的内容</span></span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">this</span>.msg;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">fun</span><span class="params">()</span></span>&#123;</span><br><span class="line">        Inner in = <span class="keyword">new</span> Inner(<span class="keyword">this</span>);</span><br><span class="line">        in.print();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Inner</span></span>&#123;</span><br><span class="line">    <span class="keyword">private</span> Outer out;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">Inner</span><span class="params">(Outer out)</span></span>&#123;</span><br><span class="line">        <span class="keyword">this</span>.out= out;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">()</span></span>&#123;</span><br><span class="line">        System.out.println(<span class="keyword">this</span>.out.getMsg());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Demo</span> </span>&#123;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String args[])</span></span>&#123;</span><br><span class="line">        Outer out = <span class="keyword">new</span> Outer();</span><br><span class="line">        out.fun();</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>实际上折腾了半天目的就是来访问外部类中的私有属性，特别复杂。</p>
<p>实际上对于内部类的操作远远不止于此：</p>
<blockquote>
<p>1.通过以上的代码可以发现，当前内部类的访问必须通过外部类的方法才可以完成。如果不想通过外部类访问进行调用，想在程序外部调用，那么就必须按照如下的形式进行内部类的实例化对象创建：</p>
</blockquote>
<pre><code>语法：`外部类.内部类 内部类对象=new 外部类.new 内部类();`
</code></pre><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> 内部类;</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Other</span></span>&#123;<span class="comment">//定义了一个外部类</span></span><br><span class="line">    <span class="keyword">private</span> String msg = <span class="string">"hello world!!"</span>;</span><br><span class="line">    <span class="comment">//+++++++++++++++++++++++++++++++++++</span></span><br><span class="line">    <span class="class"><span class="keyword">class</span> <span class="title">Inner</span></span>&#123;<span class="comment">//定义了一个内部类</span></span><br><span class="line">        <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">()</span></span>&#123;<span class="comment">//定义了一个普通方法</span></span><br><span class="line">            System.out.println(msg);<span class="comment">//调用msg属性</span></span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">//+++++++++++++++++++++++++++++++++++</span></span><br><span class="line">    <span class="comment">//定义一个外部类方法，这个方法负责产生内部类对象并且调用print()方法</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">fun</span><span class="params">()</span></span>&#123;</span><br><span class="line">        Inner in = <span class="keyword">new</span> Inner();</span><br><span class="line">        in.print();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Demo</span> </span>&#123;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String args[])</span></span>&#123;</span><br><span class="line">        <span class="comment">//声明内部类对象</span></span><br><span class="line">        Other.Inner in = <span class="keyword">new</span> Other().new Inner();</span><br><span class="line">        in.print();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>之所以要先进行外部类对象实例化，主要的问题在于此时的外部类中存在有属性，这些属性只有在开辟实例化对象之后才能够被访问。</p>
<blockquote>
<p>2.如果现在一个内部类只想被外部类所使用，即：不希望直接产生内部类的实例化对象，那么可以使用private定义。</p>
</blockquote>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> 内部类;</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Other</span></span>&#123;<span class="comment">//定义了一个外部类</span></span><br><span class="line">    <span class="keyword">private</span> String msg = <span class="string">"hello world!!"</span>;</span><br><span class="line">    <span class="comment">//+++++++++++++++++++++++++++++++++++</span></span><br><span class="line">    <span class="keyword">private</span> <span class="class"><span class="keyword">class</span> <span class="title">Inner</span></span>&#123;<span class="comment">//定义了一个内部类</span></span><br><span class="line">        <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">()</span></span>&#123;<span class="comment">//定义了一个普通方法</span></span><br><span class="line">            System.out.println(msg);<span class="comment">//调用msg属性</span></span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">//+++++++++++++++++++++++++++++++++++</span></span><br><span class="line">    <span class="comment">//定义一个外部类方法，这个方法负责产生内部类对象并且调用print()方法</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">fun</span><span class="params">()</span></span>&#123;</span><br><span class="line">        Inner in = <span class="keyword">new</span> Inner();</span><br><span class="line">        in.print();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Demo</span> </span>&#123;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String args[])</span></span>&#123;</span><br><span class="line">        Other other = <span class="keyword">new</span> Other();</span><br><span class="line">        other.fun();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<blockquote>
<p>3.在进行属性访问的时候我们都要习惯性的加上this，所以如果想要在内部类中明确的使用this，那么语法形式应该变为<code>外部类.this.属性</code>这就表示外部类当前对象的属性。</p>
</blockquote>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> 内部类;</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Other</span></span>&#123;<span class="comment">//定义了一个外部类</span></span><br><span class="line">    <span class="keyword">private</span> String msg = <span class="string">"hello world!!"</span>;</span><br><span class="line">    <span class="comment">//+++++++++++++++++++++++++++++++++++</span></span><br><span class="line">    <span class="keyword">private</span> <span class="class"><span class="keyword">class</span> <span class="title">Inner</span></span>&#123;<span class="comment">//定义了一个内部类</span></span><br><span class="line">        <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">()</span></span>&#123;<span class="comment">//定义了一个普通方法</span></span><br><span class="line">            System.out.println(Other.<span class="keyword">this</span>.msg);<span class="comment">//调用msg属性</span></span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">//+++++++++++++++++++++++++++++++++++</span></span><br><span class="line">    <span class="comment">//定义一个外部类方法，这个方法负责产生内部类对象并且调用print()方法</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">fun</span><span class="params">()</span></span>&#123;</span><br><span class="line">        Inner in = <span class="keyword">new</span> Inner();</span><br><span class="line">        in.print();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Demo</span> </span>&#123;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String args[])</span></span>&#123;</span><br><span class="line">        Other other = <span class="keyword">new</span> Other();</span><br><span class="line">        other.fun();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<h1 id="static-定义内部类"><a href="#static-定义内部类" class="headerlink" title="static 定义内部类"></a>static 定义内部类</h1><p>内部类使用了static进行了定义，那么就表示其就是一个外部类的形式但是这个外部类的名称就是<code>外部类.内部类</code>,同时该内部类只允许访问外部类中的static操作。</p>
<p>范例：使用static定义内部类</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> 内部类<span class="keyword">static</span>;</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Outer</span></span>&#123;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> String msg = <span class="string">"hello world"</span>;</span><br><span class="line">    <span class="keyword">static</span> <span class="class"><span class="keyword">class</span> <span class="title">Inner</span></span>&#123;<span class="comment">// 内部类=“外部类”</span></span><br><span class="line">        <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">()</span></span>&#123;</span><br><span class="line">            <span class="comment">//此时只能使用外部类中的static操作</span></span><br><span class="line">            System.out.println();</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Demo</span> </span>&#123;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String args[])</span></span>&#123;</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>如果要想操作这个外部类那么就应该使用如下语法：</p>
<ul>
<li>实例化对象：<code>外部类.内部类 内部类对象= new 外部类.内部类()</code></li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> 内部类<span class="keyword">static</span>;</span><br><span class="line"></span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Outer</span></span>&#123;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> String msg = <span class="string">"hello world"</span>;</span><br><span class="line">    <span class="keyword">static</span> <span class="class"><span class="keyword">class</span> <span class="title">Inner</span></span>&#123;<span class="comment">// 内部类=“外部类”</span></span><br><span class="line">        <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">()</span></span>&#123;</span><br><span class="line">            <span class="comment">//此时只能使用外部类中的static操作</span></span><br><span class="line">            System.out.println(msg);</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Demo</span> </span>&#123;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String args[])</span></span>&#123;</span><br><span class="line">        Outer.Inner in = <span class="keyword">new</span> Outer.Inner();</span><br><span class="line">        in.print();</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>以后在开发之中一定会见到类似的概念。</p>
<h1 id="在方法中定义内部类"><a href="#在方法中定义内部类" class="headerlink" title="在方法中定义内部类"></a>在方法中定义内部类</h1><p>理论上内部类可以定义在类内部的任何位置，这就包括了：类中，方法中，代码块中。不过如果从实用的角度来讲，在方法中定义一个内部类的形式是最多的。</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> 内部类方法中;</span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">Outer</span></span>&#123;</span><br><span class="line">    <span class="keyword">private</span> String msg = <span class="string">"helloworld"</span>;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">fun</span><span class="params">(<span class="keyword">int</span> num)</span></span>&#123;</span><br><span class="line">        <span class="class"><span class="keyword">class</span> <span class="title">Inner</span></span>&#123;</span><br><span class="line">            <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">print</span><span class="params">()</span></span>&#123;</span><br><span class="line">                System.out.println(Outer.<span class="keyword">this</span>.msg);</span><br><span class="line">                System.out.println(num);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">new</span> Inner().print();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Demo</span> </span>&#123;</span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String args[])</span></span>&#123;</span><br><span class="line">        <span class="keyword">new</span> Outer().fun(<span class="number">100</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>此时的代码在jdk1.8是正常的，但是在jdk1.8之前肯定是错误的。</p>
<p>在jdk1.7及以前，如果一个内部类定义在了方法之中，那么如果该内部类想要访问方法中的参数，这个参数必须使用final定义，而在jdk1.8之后为了推广他的函数式编程，所以将这一局限取消了。</p>
<p>内部类的使用暂时不作为你设计的首选。</p>
<ul>
<li>破坏了程序的结构；</li>
<li>方便进行私有属性的访问；（外部类也可以访问内部类的私有属性）</li>
<li>如果以后发现类名称上出现了<code>.</code>,应该立刻想到是内部类的概念；</li>
</ul>

      
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              <div class="post-toc-content"><ol class="nav"><li class="nav-item nav-level-1"><a class="nav-link" href="#内部类的基本概念"><span class="nav-number">1.</span> <span class="nav-text">内部类的基本概念</span></a></li><li class="nav-item nav-level-1"><a class="nav-link" href="#static-定义内部类"><span class="nav-number">2.</span> <span class="nav-text">static 定义内部类</span></a></li><li class="nav-item nav-level-1"><a class="nav-link" href="#在方法中定义内部类"><span class="nav-number">3.</span> <span class="nav-text">在方法中定义内部类</span></a></li></ol></div>
            

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